CN111664060A

CN111664060A - Offshore wind turbine foundation anti-scouring structure

Info

Publication number: CN111664060A
Application number: CN202010462182.XA
Authority: CN
Inventors: 曹人靖; 刘周明
Original assignee: Shenzhen Union Clean Energy Research Institute; Southern University of Science and Technology
Current assignee: Shenzhen University; Southern University of Science and Technology
Priority date: 2020-05-27
Filing date: 2020-05-27
Publication date: 2020-09-15

Abstract

The invention provides an offshore wind turbine foundation anti-scouring structure which comprises an annular pile skirt, wherein the annular pile skirt is sleeved outside a pile foundation and fixed on a sea bed surface, and the annular pile skirt comprises a mounting hole for the pile foundation to penetrate through, a scouring surface and a buffer surface, the scouring surface extends from the mounting hole to the sea bed surface, the height of the scouring surface is gradually reduced, and the buffer surface is arranged at the joint of the scouring surface and the sea bed surface. According to the anti-scouring structure for the offshore wind turbine foundation, the inclined plane provided with the scouring surface and the buffering surface on the annular pile skirt is in gradient fit with the speed change of seawater generated by ocean current or tide, so that the speed of the ocean current or tide reaching the annular pile skirt is basically consistent, the ocean current can be weakened to the maximum extent to generate pile front vortex near a pile foundation, and a scouring pit formed by the vortex is avoided; the anti-scouring structure provided by the invention has the advantages of simple structure, easiness in processing, lower construction cost, convenience in later maintenance and good anti-scouring effect, and ensures the bearing capacity of a pile foundation and the running reliability of a fan.

Description

Offshore wind turbine foundation anti-scouring structure

Technical Field

The invention relates to the technical field of ocean engineering structures, in particular to an anti-scouring structure for an offshore wind turbine foundation.

Background

Offshore wind resources are rich, the change of wind speed along with height is small, the turbulence intensity is low, the sea level friction is small, the fatigue load acting on the wind generating set is also small, the interference of noise, birds and electromagnetic waves on offshore wind power generation is small, and land resources on land can not be occupied. Therefore, offshore wind power generation becomes the fastest-developing green energy technology in the world.

The influence of the obstruction of the pile foundation and the speed gradient of ocean current easily produces scouring around the pile foundation of offshore construction, takes away silt around the pile foundation, leads to the reduction of pile body bearing capacity, basis slope, can produce the serious consequence that the basis wholly collapses even.

In order to improve the problem that the foundation pile of the offshore wind turbine foundation is flushed, the existing foundation has the following methods:

1. concrete is put in or gravels are paved in a certain range around the pile foundation, the rigidity of the solidified concrete is higher, the pile foundation can be guaranteed not to be influenced by scouring in the service life, but the putting area of the concrete is larger, the cost is higher, and the later maintenance is more difficult; and lay the grit and form the scour prevention effect of scouring surface in the short time better, but inevitable existence clearance between the grit, along with the effect of the daily accumulation of ocean current and morning and evening tides, silt of grit below still can be washed away, the stone is destroyed and is leaded to the stone to sink into silt particle layer and cause the protection to weaken, need constantly put in the grit in order to maintain the scour prevention effect and maintain and lead to the maintenance cost in later stage higher.

2. The anti-scouring structure with the sill is arranged on the basis of the pile foundation, the flow velocity of bottom ocean current is reduced through the stepped structure of the sill, the pile foundation is prevented from being scoured by the bottom flow velocity, and the horseshoe vortex formed by the ocean current near the pile foundation is destroyed by the stepped structure of the sill. However, the anti-scouring structure with the sill structure can cause silt to be carried by the overflow plate arranged above the sill to fall into silt along with the lapse of time in the long-term use process, so that gravels are accumulated in the sill below, the stepped structure disappears, and the horseshoe vortex formed by the erosion cannot be destroyed.

Disclosure of Invention

The invention aims to solve the problems of high investment cost and high later maintenance cost in the scheme of paving concrete or gravel in the existing offshore wind turbine foundation anti-scouring structure, and overcomes the defect that the step-shaped structure of a bottom sill disappears and the horseshoe vortex formed by ocean current cannot be destroyed because the gravel is easy to deposit in the bottom sill in the anti-scouring structure with the bottom sill matched with an overflowing plate structure, so that the offshore wind turbine foundation anti-scouring structure is provided.

The technical scheme adopted by the invention for solving the technical problems is as follows: the utility model provides an offshore wind turbine foundation scour prevention structure, locates the pile foundation outside and is fixed in the cyclic annular stake skirt on the sea bed surface including the cover, cyclic annular stake skirt including supply the pile foundation wears to establish the mounting hole, by the mounting hole extends to the scouring face that highly reduces gradually of sea bed surface with set up in the scouring face with the buffering face of sea bed surface junction.

Further, the lower diameter of the annular pile skirt is 3-4 times of the outer diameter of the pile foundation.

Furthermore, a first included angle is formed between the flushing surface and the sea bed surface, a second included angle is formed between the buffering surface and the sea bed surface, and the second included angle is larger than the first included angle and smaller than 90 degrees.

Specifically, the first included angle is equal to or greater than 13 °.

Furthermore, the anti-scouring structure further comprises at least two spoilers fixed on the annular pile skirt, wherein the spoilers are vertical to the scouring surface in the vertical direction and vertical to the outer circumferential surface of the pile foundation in the horizontal direction.

Specifically, the height from the highest position of the spoiler to the sea bed surface is 0.7-1 time of the outer diameter of the pile foundation.

Specifically, the length of the spoiler in the radial direction of the annular pile skirt is 1-2.5 times of the outer diameter of the pile foundation.

Specifically, the side surface of one side of the spoiler is attached to the outer circumferential surface of the pile foundation.

Specifically, six spoilers are uniformly distributed on the flushing surface along the circumferential direction.

Furthermore, each spoiler is provided with at least one spoiler hole, and the spoiler holes are through holes penetrating through the spoilers.

The anti-scouring structure of the offshore wind turbine foundation provided by the invention has the beneficial effects that: the bottom of the pile foundation is provided with an annular pile skirt, the annular pile skirt is provided with a buffer surface and a buffer surface, and the inclined surface of the buffer surface are in gradient fit with the speed change of seawater generated by ocean current or tide, so that the speed of the ocean current or tide reaching the annular pile skirt is basically consistent, the ocean current or tide can be reduced to the maximum extent to generate pile front vortex near the pile foundation, and a scouring pit formed by the vortex is avoided; meanwhile, spoilers are further arranged on the annular pile skirt, so that the resistance around the pile foundation is increased, the vortex generation direction perpendicular to the pile foundation is separated, the flow velocity is reduced, and the purpose of dispersing the vortex amount is achieved; the annular pile skirt and the spoiler act together to provide a good anti-scouring effect for the pile foundation; the anti-scouring structure provided by the invention has the advantages of simple structure, easiness in processing, lower construction cost and convenience in later maintenance, and can prevent the pile foundation from being scoured by eddy currents by stopping the flow velocity of ocean currents or tides around the pile foundation, thereby ensuring the bearing capacity of the pile foundation and the running reliability of a fan.

Drawings

Fig. 1 is a schematic perspective view of an annular pile skirt in an anti-erosion structure of an offshore wind turbine foundation according to a first embodiment of the present invention;

fig. 2 is a full sectional view of an annular pile skirt in an anti-erosion structure of an offshore wind turbine foundation according to a first embodiment of the present invention;

fig. 3 is a schematic view of an anti-erosion structure of an offshore wind turbine foundation installed on a pile foundation according to a first embodiment of the present invention;

fig. 4 is a full sectional view of an annular pile skirt in an anti-erosion structure of an offshore wind turbine foundation according to a second embodiment of the present invention.

In the figure: 100. 100 '-anti-erosion structure, 10' -annular pile skirt, 11-mounting hole, 12-flushing surface, 13-buffer surface, 20-spoiler, 21-first side surface, 22-second side surface, 23-spoiler hole, 200-pile foundation, 300-sea bed surface, D-pile foundation outer diameter, D1-lower diameter of annular pile skirt, height of H1-spoiler from sea bed surface, length of L1-spoiler, distance of L2-spoiler from buffer surface, alpha-first included angle and beta-second included angle.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Referring to fig. 1 to 3, in the offshore wind turbine foundation erosion prevention structure 100 according to the first embodiment of the present invention, the erosion prevention structure 100 is disposed at the bottom of a pile foundation 200 of an offshore wind turbine, and through the erosion prevention structure 100, generation of pile forward vortex at the pile foundation 200 is reduced to the greatest extent, so as to effectively prevent a washout pit from being formed at the bottom of the pile foundation 200, ensure a bearing capacity of the pile foundation 200 on a sea bed surface 300, and prevent inclination of the pile foundation 200.

Further, as shown in fig. 3, an anti-erosion structure 100 for a foundation of an offshore wind turbine according to a first embodiment of the present invention includes an annular pile skirt 10 that is sleeved outside a pile foundation 200 and fixed to a seabed surface 300, and at least two spoilers 20 that are fixed to the annular pile skirt 10. In the present embodiment, as shown in fig. 1, six spoilers 20 are provided on the annular pile skirt 10 and are uniformly distributed along the circumferential direction of the annular pile skirt 10. The erosion prevention structure 100, the annular pile skirt 10 may meet the velocity gradient existing in the ocean current or tidal flow at the pile foundation 200, so that the ocean current is almost stagnant. The swirl flow passing through the spoiler 20 not only facilitates the separation of the flow direction of the swirl flow, but also consumes the flow rate of the swirl around the pile foundation 200 to achieve the purpose of dispersing the swirl amount.

Specifically, as shown in fig. 2, the annular pile skirt 10 includes a mounting hole 11 through which the pile foundation 200 can be inserted, a flushing surface 12 extending from the mounting hole 11 to the seabed surface 300 and having a gradually decreasing height, and a buffer surface 13 disposed at a connection portion between the flushing surface 12 and the seabed surface 300. The annular pile skirt 10 is fitted around the outer circumferential surface of the pile foundation 200 and is located at the joint between the pile foundation 200 and the seabed surface 300. The diameter of the mounting hole 11 is determined by the machining accuracy and the mounting accuracy. On the premise of ensuring the processing precision and the installation precision, the aperture of the installation hole 11 is equal to the pile foundation outer diameter D. The aperture of the mounting hole 11 is 10mm-20mm larger than the pile foundation outer diameter D according to different processing precision and mounting precision. In this embodiment, as shown in fig. 2, the annular pile skirt 10 is disposed on the seabed surface 300 in a conical structure, and the annular pile skirt 10 has two inclined surfaces with different angles, a brushing surface 12 diverging outwardly from the outer circumferential surface of the pile foundation 200, and a cushioning surface 13 diverging outwardly from the brushing surface 12. The height of the cushioning surface 13 and the flushing surface 12 gradually increases from the surface 300 of the sea bed upwards. In the anti-erosion structure 100 provided by the present invention, the two-stage inclined planes of the erosion face 12 and the erosion face 13 on the annular pile skirt 10 are substantially attached to the velocity gradient of the ocean current that can collide with the periphery of the pile foundation 200, so that the ocean current can almost reach the annular pile skirt 10 from top to bottom at the same time, thereby playing a role of synchronously stopping the ocean current flow, and further maximally weakening the pile forward vortex generated at the pile foundation 200. Meanwhile, the height of the brushing surface 12 is gradually reduced from top to bottom, so that the ocean current which firstly reaches the pile foundation 200 above generates resistance when flowing downwards, and the ocean current is not easy to flow downwards, thereby reducing the downward impact force of the front vortex of the pile, and avoiding the generation of a front pit at the annular pile skirt 10 due to the influence of the ocean current or tide. In the offshore wind turbine foundation anti-scouring structure 100 provided by the invention, the scouring surface 12 and the scouring surface 13 on the annular pile skirt 10 are both designed to be inclined surfaces, so that the problem of failure caused by sand accumulation and sinking caused by long-term use can be avoided in the long-term use process, and the later maintenance cost is low.

Further, as shown in fig. 2, the lower diameter D1 of the annular pile skirt 10 is 3 to 4 times the pile outer diameter D. The annular pile skirt 10 is a rigid structure resistant to seawater erosion, and in the first embodiment provided by the invention, the annular pile skirt 10 is a solid structure, so that the rigidity and stability of the brushing surface 12 and the buffering surface 13 can be ensured to the greatest extent, and the deformation of the brushing surface 12 and the buffering surface 13 caused by the impact of ocean currents is avoided. And the size of the lower diameter D1 of the annular pile skirt 10 is determined by the velocity gradient existing in the ocean current or tide where the pile foundation 200 is installed. The larger the velocity gradient formed by the ocean current from top to bottom, the smaller the lower diameter D1 of the corresponding annular skirt 10. The smaller the velocity gradient formed by the ocean current from top to bottom, the larger the lower diameter D1 of the corresponding annular skirt 10.

Further, as shown in fig. 2, a first included angle α is formed between the brushing surface 12 of the annular pile skirt 10 and the seabed surface 300, a second included angle β is formed between the buffering surface 13 and the seabed surface 300, and the second included angle β is greater than the first included angle α and smaller than 90 °. A first angle alpha formed between the scouring surface 12 and the seabed surface 300 is greater than or equal to 13 deg. That is, α is not less than 13 °, so that the flushing surface 12 can meet the velocity gradient of the ocean current in the height direction, and the flushing surface 12 can effectively stop the flow of the ocean current. Meanwhile, the alpha is more than beta and less than 90 degrees, so that a certain transition can be formed between the buffer surface 13 and the scouring surface 12, and the buffer surface 13 can better meet the speed gradient change of ocean current close to the position 300 of the ocean bed surface. The specific parameters of the first included angle alpha and the second included angle beta are determined by the marine environmental conditions in which the pile foundation 200 is installed. The specific inclination of the brushing surface 12 and the cushioning surface 13 is determined by pre-measuring the marine environment at which the pile 200 is installed.

Further, the erosion prevention structure 100 of the present invention further comprises at least two spoilers 20 fixed to the brushing surface 12, wherein the spoilers 20 are configured to further stop the flow of the pre-pile vortex at the pile foundation 200. The number and the arrangement mode of the spoilers 20 are determined by the environment where the pile foundation 200 is installed. The spoilers 20 may be evenly distributed along the circumferential direction of the annular skirt 10 as shown in fig. 1. In the present embodiment, six spoilers 20 are uniformly distributed on the brushing surface 12 of the annular pile skirt 10 along the circumferential direction. Of course, the distribution of the spoilers 20 may be distributed on the brushing surface 12 of the annular pile skirt 10 on one side where ocean currents are likely to occur and on the other side, the distribution may be reduced. The distribution number of the spoilers 20 is determined by the flow speed of the pile tip vortex generated at the pile foundation 200. If the flow rate of the pile forward vortex is fast, the number of spoilers 20 can be correspondingly increased, and if the flow rate is slow, at least two can be provided to further impede the flow of the vortex. Generally, 2 to 10 spoilers 20 can be distributed on the annular pile skirt 10 to stop the flow of the vortex, and if the spoilers 20 are arranged densely, the spoilers cannot play a role in stopping the flow of the vortex.

Specifically, the spoiler 20 provided in the erosion prevention structure 100 provided by the present invention is a steel plate having a certain thickness, and the spoiler 20 may be integrally formed with the annular pile skirt 10, or may be fixed to the erosion surface 12 of the annular pile skirt 10 by welding, riveting, screwing, or the like. When the spoiler 20 is fixed, it is only necessary to ensure that the spoiler 20 is vertically disposed perpendicular to the brushing surface 12 and horizontally disposed perpendicular to the outer circumferential surface of the pile foundation 200. The spoilers 20 are arranged vertically perpendicular to the flushing surface 12, i.e. each spoiler 20 is arranged vertically perpendicular to the sea floor surface 300 and adjacent spoilers 20 are parallel to each other. The spoiler 20 is disposed perpendicular to the outer circumferential surface of the pile foundation 200 in the horizontal direction, so that the spoiler 20 reduces the vorticity of the vortex perpendicular to the pile foundation 200, and the vortex flows are separated in the direction after flowing through the spoiler 20, and a part of the vortex surrounding the pile foundation 200 is carried away by the external ocean current and a part of the vortex is hit and consumed by the disposition of the spoiler 20. The provision of the spoiler 20 on the annular pile skirt 10 serves to further disperse the amount of the pile forward vortex around the pile foundation 200.

Specifically, as shown in fig. 2, the height H1 of the spoiler 20 from the maximum position to the sea bed surface 300 is 0.7 to 1 times the outer diameter of the pile foundation 200. The height of the spoiler 20 and the annular pile skirt 10 is H1, which is the height from the sea floor surface 300 of the highest part of the spoiler 20, and H1 is determined by the surrounding sea environment of the pile foundation 200. The height of the spoiler 20 is substantially the same as the height of the annular pile skirt 10, and if the height H1 of the highest position of the spoiler 20 from the sea floor surface 300 is greater, the thickness and rigidity of the spoiler 20 should be increased to prevent the spoiler 20 from being deformed due to the impact of the ocean current. If the height H1 of the spoiler 20 from the sea floor surface 300 is small at the highest position, the function of preventing the vortex around the pile foundation 200 cannot be performed.

Specifically, as shown in fig. 2, the length L1 of the spoiler 20 in the radial direction of the annular pile skirt 10 is 1 to 2.5 times the pile outer diameter D. The length L1 of the spoiler 20 is too large, which requires a higher thickness of the spoiler 20, i.e., a rigidity of the spoiler 20, resulting in an increase in weight and cost of the spoiler 20. The length L1 of the spoiler 20 is too small, and the length L1 provided on the brushing surface 12 is not sufficient, and thus the spoiler cannot sufficiently function to block the flow of the ocean current around the pile foundation 200. Therefore, the length L1 of the spoiler 20 is 1 to 2.5 times the pile outer diameter D, and the specific value is determined by the installation environment of the pile foundation 200.

Further, as shown in fig. 2 and 3, the side surface 21 of one side of the spoiler 20 is attached to the outer circumferential surface of the pile foundation 200, and the distance L2 between the side surface 22 of the other side of the spoiler 20 and the buffering surface 13 is 0 to 0.5 times the length L1 of the spoiler 20. That is, the spoiler 20 may extend from the outer circumferential surface of the pile foundation 200 to the sea bed surface 300, or may be shortened to be disposed only on the brushing surface 12 as needed. It is only necessary to ensure that the length L1 of the spoiler 20 can cover the vortex flow passing place of the outer circumference of the pile foundation 200.

Further, as shown in fig. 1, at least one spoiler 23 is disposed on each spoiler 20, and the spoiler 23 is a through hole penetrating through the spoiler 20. The spoiler hole 23 may be a plurality of through holes regularly distributed on the spoiler 20, or may be a through hole disposed on the spoiler 20 as shown in fig. 1. The spoiler holes 23 are provided to further function as a spoiler swirling flow direction and a flow velocity, and the manner of their arrangement and the number of arrangement are not particularly limited.

Referring to fig. 4, an anti-erosion structure 100' for a foundation of an offshore wind turbine is provided according to a second embodiment of the present invention. The second embodiment of the present invention is different from the first embodiment in that the inside of the annular pile skirt 10 'may be configured as a hollow structure on the premise of ensuring that the overall rigidity of the buffer surface and the buffer surface of the annular pile skirt 10' is not deformed by the ocean current. The hollow structure of the annular pile skirt 10 ' can reduce the weight of the whole anti-scouring structure 100 ', and reduce the cost as much as possible on the premise of ensuring the anti-scouring effect of the anti-scouring structure 100 '.

The invention provides an offshore wind turbine foundation anti-scouring structure 100 (100'), wherein the bottom of a pile foundation 200 is provided with an annular pile skirt, the annular pile skirt is provided with a buffer surface 12 and a buffer surface 13, and the inclined surface of the buffer surface 12 and the inclined surface of the buffer surface 13 are in gradient fit with the speed change of seawater generated by ocean current or tide, so that the speed of the seawater generated by the ocean current or tide reaching the annular pile skirt 10 is basically consistent, the ocean current or the tide can be weakened to the maximum extent to generate pile front vortex near the pile foundation 200, and a scouring pit formed by the vortex is avoided; meanwhile, the annular pile skirt is also provided with the spoilers 20, so that the resistance around the pile foundation 200 is increased, the vortex generation direction vertical to the pile foundation 200 is separated, the flow velocity is reduced, and the purpose of dispersing the vortex amount is achieved; the annular pile skirt 10 and the spoiler 20 act together to provide a good anti-scouring effect for the pile foundation 200; the anti-scouring structure provided by the invention has the advantages of simple structure, easiness in processing, lower construction cost and convenience in later maintenance, prevents the pile foundation 200 from being scoured by eddy currents by stopping the flow velocity of ocean currents or tides around the pile foundation 200, ensures the bearing capacity and the operation reliability of the pile foundation 200 and prolongs the service life of the pile foundation 200.

The present invention is not limited to the above preferred embodiments, and any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The utility model provides an offshore wind turbine foundation scour prevention structure, its characterized in that locates the pile foundation outside and is fixed in the cyclic annular stake skirt on the sea bed surface including the cover, cyclic annular stake skirt including can supply the mounting hole that the pile foundation wore to establish, by the mounting hole extends to the scouring face that highly reduces gradually of sea bed surface with set up in the scouring face with the buffering face of sea bed surface junction.

2. An offshore wind turbine foundation erosion prevention structure as recited in claim 1, wherein the lower diameter of the annular pile skirt is 3-4 times the pile foundation outer diameter.

3. An offshore wind turbine foundation anti-erosion structure according to claim 1, wherein a first included angle is formed between the erosion surface and the seabed surface, a second included angle is formed between the buffer surface and the seabed surface, the second included angle is larger than the first included angle and smaller than 90 °.

4. An offshore wind turbine foundation erosion prevention structure as recited in claim 3, wherein said first included angle is equal to or greater than 13 °.

5. An offshore wind turbine foundation erosion prevention structure of claim 1, further comprising at least two spoilers fixed to the annular pile skirt, wherein the spoilers are vertically arranged perpendicular to the erosion surface and horizontally arranged perpendicular to an outer circumferential surface of the pile foundation.

6. An offshore wind turbine foundation erosion prevention structure as recited in claim 5, wherein the height of the highest part of the spoiler from the surface of the sea bed is 0.7-1 times the outer diameter of the pile foundation.

7. An offshore wind turbine foundation erosion prevention structure in accordance with claim 5, wherein the length of the spoiler in the radial direction of the annular pile skirt is 1 to 2.5 times the pile outer diameter.

8. An anti-scouring structure for an offshore wind turbine foundation according to claim 7, wherein a side surface of one side of the spoiler is fitted to an outer circumferential surface of the pile foundation.

9. An offshore wind turbine foundation erosion prevention structure as recited in claim 5, wherein six said spoilers are evenly distributed on said scouring surface along a circumferential direction.

10. An offshore wind turbine foundation erosion prevention structure according to any one of claims 5 to 9, wherein each spoiler is provided with at least one spoiler, and the spoiler is a through hole penetrating through the spoiler.